Gustave bay



UNITED STATES PATENT OFFICE.

GUSTAVE BAY, OF SURESNES, NEAR PARIS, FRANCE.

PHOTOGRAPHIC COPYING PROCESS.

SPECIFICATION forming part of Letters Patent No. 394,437, dated December 11, 1888.

Application filed May 3, 1888. Serial No. 272,694. (No specimens.) Patented in France May 19, 1885, No. 169,013 in Belgium May 20, 1886, No. 73,204, and in England September 8, 1887, No. 12,168.

To aZZ whom it. may concern.-

Be it known that I, GUSTAVE BAY, a citizen of France, and a resident of Suresnes, near Paris, France, have invented a new or Improved Process for Rapidly Obtaining Positi ve Black-Line Copies from Positive Tracings orNegatives by the Action of Light, (for which I have obtained a British patent, No. 12,168, September 8, 1887 French patent, No. 169,013, May 19, 1885, and Belgian patent, No. 73,204, May 20, 1886,) of which the following is a specification.

The process is based as under, first, on the reduction, by the action of light, of the salts of iron in the presence of organic acids, (citric, tartaric, &c.;) second, on the formation of a brownish precipitate produced by these salts in the presence of the, yellow or red prussiates of potash, combined with certain yellow, red, and brown vegetable coloringmatters and the extracts and lakes of such matters; third, on the formation of a precipitate of coloring-matter varying from red to dark brown, produced by hydratic alkaline matterssuch, for instance, as soda, potash, ammonia, lime, &c., and the salts derived from themin the presence of a decoction or infusion of such coloring-matters or of their extracts.

I prepare a paper with a solution of gumarabic, tartaric acid, and perchloride of iron. I leave it to dry, and afterward I expose it in a photographic frame under an india-ink tracing or any other suitable negative. On taking it out of the frame I develop the copy upon a bath of water saturated with prussiate of potash, after which I place it upon a bath consisting of a decoction or infusion of coloring-matter. \Vhen the lines of the copy are quite black, I wash the copy under a watertap, after which I dip the sheet in abath consisting of a salt of soda, ammonia, potash, &c. The degree of saturation is a matter of little importance, provided the salt is neutral and has an acid action with an alkaline reaction. The acid clears the background, while the alkaline matter destroys the blue produced by the salt of iron and the prussiate and the copy by means of the precipitate with the coloring-matter, either in violet,brown, or black, according to the salt used and the duration of the bath. I finally wash under a tap with brush and plenty of Water. The baths may be used until ineffective. I can also obtain the copies bya single bath of about half prussiate and half coloring-matter, the development of the copy being my guide in the matter.

On taking the sheet out of the frame I place it for five or ten minutes upon this bath, after which I wash it with a brush. The copy will then appear black upon a yellowish ground, which I can subsequently clean and bleach by means of a bath of alkaline salt.

What I claim as my invention, and desire to secure by Letters Patent, is-

The method described of obtaining a direct positive black-line copy on a white ground, said method consisting in exposing a paper sensitized by a solution of gum-arabic, tartaric acid, and iron perchloride to the action of light, said paper being covered by the tracing or drawing to be copied, then developing the copy upon a bath of water saturated with prussiate of potash, then placing it upon a bath consisting of a decoction or infusion of coloring-matter, washing, and then dipping in a bath consisting of a neutral salt or salts having an acid action and an alkaline reaction, substantially as described.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

GUSTAVE BAY.

\Vitnesses:

LOMBARD RONNEVILLE, CH. BROWN. 

